Description of the Related Art
FIG. 1 is a schematic view of a prior art lamp housing 10. The lamp housing 10 contains a lamp 26 (also called a “light source 26”) which projects diverging light having a variety of wavelengths from the interior 24 of the lamp 26. Some of the light is directed toward a reflective mirror 16 which reflects the light toward a band-pass filter 20. In some prior art embodiments, the mirror 16 is planar (as shown), whereas in other prior art embodiments the mirror 16 is curved. However, in all prior art embodiments, at least some of the light reflected by the mirror 16 is redirected back toward the light source 26.
The purpose of a band-pass filter in an optical system is to reflect light in a specific range of wavelengths and to transmit light of a different set of wavelengths. A particular type of band-pass filter, often referred to as a “cold mirror,” is used to provide good reflection of light having wavelengths in a particular range and to transmit light outside of that range. For example, one type of cold mirror reflects light having wavelengths between about 200 nm to about 450 mm (i.e., ultraviolet (“UV”) light and the lower end of the visible light spectrum) and transmits light having wavelengths above about 450 nm, i.e., light which includes most visible light and infrared (“IR”) light. Similarly, another type of band-pass filter, i.e., a hot mirror, transmits light having wavelengths between about 200 nm to about 450 nm (i.e., UV light and the lower end of the visible light spectrum) and reflects light having wavelengths above about 450 nm, i.e., light which includes most visible light and IR light.
Band-pass filters are used to separate light into usable and unusable light. For example, a cold mirror may be used to separate light into UV light and visible/IR light. The UV light may be reflected toward a material, such as an object or web 8, that is to be cured via a curing application. By way of contrast, the visible/IR light may be transmitted through the cold mirror (i.e., it is not directed toward the curing application at hand) to prevent unnecessary and unwanted heating of the materials that are to be cured.
The band-pass filter 20 is typically adapted to reflect light having wavelengths which fall within a specified range and to transmit light having wavelengths outside of that range. For example, in curing applications, if a cold mirror is used for the band-pass filter 20, it may reflect light having wavelengths between about 200 nm to about 450 nm (e.g., UV light) and transmit light outside of this range, including visible light and IR light. The light which is reflected by the cold mirror may pass through a protective window 22 and may be used in applications calling for a particular type of light, e.g., UV light. Similarly, if a hot mirror is used for the band-pass filter 20, it may transmit light having wavelengths between about 200 nm to about 450 nm (e.g., ultraviolet light) and reflect light outside of this range, including visible light and IR light.
As the remaining light (e.g. visible/IR) is transmitted through the band-pass filter, it may be necessary to protect people and/or items which may be harmed by exposure to this light. To address this concern, the light which is transmitted through the band-pass filter may pass through an air corridor 52 and into a solid heat sink 30, where it may be absorbed and converted into heat energy via radiant heat transfer.
Air, which is fed into the air corridor 52 via inlets 50, may be used to cool the heat sink 30. Similarly, air may be fed into the housing 10 via inlets 40. The air passing through the inlets 40 may be used to cool the light source 26, the mirror 16, and/or a set of reflective shutters 12. Further, the heat sink 30 may be designed so that its shape and cross-sectional area will allow the heat absorbed therein to be transferred to a stream of cooling air in the air corridor 52 via forced/induced convection.
Some of the light from the light source 26 is also reflected off the reflective surfaces (“shutters”) 12 toward the band-pass filter 20. The purpose of shutters 12 in a UV curing system is to gather and direct the light emitted from the lamp 26 to a two (or three) dimensional plane(s) or object(s) 8 where UV curing will take place. The shutters 12 may also be closed to prevent (or at least greatly inhibit) the light (and heat associated therewith) emitted from a lamp 26 from reaching objects 8 where UV curing will take place.
The shutters 12, which have traditionally rotated on axes 14, have inside surfaces (i.e., on the side facing the light source) which are highly polished. As a result, when an object 8 (which may be in the form of a film or label) to be cured is moved across a window 22 in the housing 10, the shutters 12 may be opened and the polished surface of the shutters 12 used to gather and direct the light toward the band-pass filter 20.
The shutters 12 also serve a heat containment function. The temperature of the light source 26 may reach from about 650° C. to about 850° C. In some embodiments, as the light source 26 is reasonably close to the moving object 8, if the object 8 is stopped while the lamp housing 10 is emitting light, it may be preferable to protect the object 8 from the heat associated with the light emitted by light source 26 by closing the shutters 12.
The shutters 12 may be opened due to their being adapted to rotate on the axes 14. In a first position (not shown in FIG. 1), the distal ends 13 of the shutters 12 approach each other, thereby substantially containing the light emitted by light source 26. In a second position, shown in FIG. 1, the distal ends 13 of the shutters 12 are separated so that the light emitted by the light source 26 can be reflected toward the band-pass filter 20.
Previously, to move the shutters 12 from a non-shutter position (also referred to as a “closed position”) to a shutter position (also referred to as an “open position”), the shutters 12 were rotated about the axes 14, such as by mechanically attaching the shutters 12 to a round drive shaft 15 (as shown in FIG. 2), which is driven by a motor (not shown) in the curing lamp housing 10. The shutter 12 contained a hole into which the shaft 15 was slid, pressed, heat fit, use of a set screw, etc. to attach the shutter 12 to the shaft 15. Further, this method of attaching the shutter 12 and the shaft 15 involved drilling into the shutter 12 and pinning the shaft 15 to it; this, however, is a time consuming operation. The shaft 15, in turn, was passed through or laid upon a surface(s) to support the shutter 12 in both static and dynamic conditions.
When the shutter 12 had to be serviced or replaced, the mechanical attachment of the shutter 12 to the shaft 15 had to be removed or disengaged. For example, if the shutter 12 and shaft 15 had been drilled and pinned, the pin 17 had to be driven out, before the shaft 15 and shutter 12 could be removed; this operation often damaged the hole in the shutter 12 to the point where it could not be reused. Similarly, if the shaft 15 has been pressed into and through a hole in the shutter 12, the shaft 15 had to be pressed back out of the shutter 12 in order for the shutter 12 to be removed. Further, if the shaft 15 had been heat fit into the shutter 12, some thermal or mechanical method had to be used to remove the shaft 15 from the shutter 12. In all these removal/disengagement methods, there existed a possibility that some of the mechanical dimensions (e.g., shape, fit, etc.) of the shaft 15 and/or the shutter 12 would change as a result of the stress (mechanical and/or thermal) which the removal/disengagement process caused.
Accordingly, what is needed is a new method and apparatus which: (a) may mechanically attach a drive shaft to the shutter; (b) may provide for easy field replacement of the shutters without inducing the aforementioned mechanical stress; and/or (c) may reduce the downtime of a curing lamp housing while a shutter is being replaced.